1. Technical Field
The present invention relates to a method of recognizing whether a display apparatus is newly connected to a main body of a computer, and more particularly to a hot-plugging method for display apparatus which is capable of judging whether a display apparatus is replaced with another by polling or interrupting.
2. Related Art
Computer systems are information handling systems that are utilized by many individuals and businesses today. A computer system can be defined as a microcomputer that includes a central processing unit (CPU), a volatile memory, a non-volatile memory such as read only memory (ROM), a display monitor, a keyboard, a mouse or other input device such as a trackball, a floppy diskette drive, a compact disc-read only memory (CD-ROM) drive, a modem, a hard disk storage device, and a printer. A computer system's main board, which is a printed circuit board known as a motherboard, is used to electrically connect these components together.
The central processing unit is often described as a microprocessor. The microprocessor is an electronic component having internal logic circuitry handling most, if not all, the data processing in the computer system. The internal logic circuitry of microprocessors is typically divided into three functional parts known as the input/output (I/O) unit, the control unit, and the arithmetic-logic unit (ALU). These three functional parts interact together and determine the power and performance of the microprocessor. The combination of the control unit and the arithmetic-logic unit can be referred to as the central processing unit. Also, the combination of the input/output unit, the control unit, and the arithmetic-logic unit can be referred to as the central processing unit.
One example of non-volatile memory is read only memory (ROM). Information stored in non-volatile memory can remain unchanged even when there is a power failure. The information stored in non-volatile memory will stay there until it is changed. Read only memory (ROM) is used to store important information such as instructions for the central processing unit (CPU). There are different types of read only memory (ROM) including electrically-erasable-programmable-read-only-memory (EEPROM) chip and flash-read-only-memory (flash-ROM). The flash-ROM can also be referred to as flash memory.
Computer systems include a basic input output system (BIOS) which is an especially important program stored in read only memory (ROM). The basic input output system (BIOS) tests a computer every time the computer is powered on. The basic input output system (BIOS) can allocate a computer system's resources automatically, making adjustments needed to accommodate new hardware. Also, the basic input output system (BIOS) governs how system board components interact.
When the computer system is powered on, the basic input output system (BIOS) immediately takes control of the computer system and its components. The first duty of the basic input output system (BIOS) is to perform a series of diagnostic routines called the power on self test (POST) routine, which ensures that every part of the computer system's hardware is functioning properly.
Consider a booting operation for a computer system using Microsoft Windows 95 as the operating system. First, a user starts the booting process by turning on a power switch to supply power to the computer system. Next, a basic input output system (BIOS) executes a power on self test (POST) to test and initialize the computer system's components. The basic input output system is software embedded on an integrated circuit located on the computer system's main board. The basic input output system also handles low-level input/output to various peripheral devices connected to the computer system. The power on self test is the part of the basic input output system that takes control immediately after the computer is turned on. The power on self test initializes the computer hardware so that an operating system can be booted (loaded). When the power on self test procedure is finished, a plug and play operation is executed if it is determined that all hardware is operating normally. A specification prepared by Microsoft and Intel that presents a mechanism to provide automatic configuration capability to Industry Standard Architecture (ISA) cards thus enabling full Plug and Play in the computer is dated 5 May 1994 and is entitled, “Plug and Play ISA Specification, Version 1.0a.” During the plug and play operation, the entire computer system is scanned for new hardware.
The plug and play operation is executed every time that the computer system is booted. Now the plug and play operation shall be described in detail. At first, a configuration manager, which manages the plug and play operation, checks to determine whether a bus is being used. That is, a bus enumerator, which is a special driver managing a bus, builds a database by gathering information on peripheral devices. Next, the configuration manager uses the database built by the bus enumerator to build a hardware tree structure and stores the hardware tree structure in a memory. The hardware tree structure indicates the composition of the hardware being used in the computer system.
Subsequently, the configuration manager operates drivers of each peripheral device indicated in the hardware tree structure. After the drivers of each peripheral device are operated, a resource arbitrator, which resolves conflicts among system resources, distributes system resources to each peripheral device. Here, system resources include interrupt request lines (IRQs), input/output port addresses, memory addresses, direct memory access (DMA) channels, and more.
Lastly, the configuration manager transmits information to the bus enumerator regarding details of the distribution of the system resources. The bus enumerator transmits information regarding allowed system resources to each peripheral device connected to the bus, thereby enabling the user to utilize the peripheral devices.
Next, when the execution of the plug and play operation is completed, system files used by the Microsoft Windows 95 operating system are executed to complete the booting process of the computer system. Then the booting process of the computer system is complete.
I believe that the plug and play operation is only performed when a computer system is booted. Therefore, I have found that it can be difficult or impossible to disconnect a first display from a computer after the computer has been booted and while the computer is operating, to connect a second display to the computer, and then to use the second display with the computer, all without rebooting the computer.